Method for conditioning semiconductor wafers and/or hybrids

ABSTRACT

The present invention provides a method for conditioning semiconductor wafers and/or hybrids having the steps: preparation of a space ( 1 ) which is at least partially enclosed and has a wafer/hybrid holding device ( 10 ) which is located therein and has the purpose of holding a semiconductor wafer and/or hybrid; and conduction of a dry fluid through the wafer/hybrid holding device ( 10 ) in order to heat-treat the wafer/hybrid holding device ( 10 ); wherein at least a portion of the fluid leaving the wafer/hybrid holding device ( 10 ) is used to condition the atmosphere within the space ( 1 ). The invention also provides a corresponding device for conditioning semiconductor wafers and/or hybrids.

The present invention relates to a method and a device for conditioningsemiconductor wafers and/or hybrids.

It is known to carry out test measurements on semiconductor waferstypically in a temperature range between −200° C. and +400° C. For theheat treatment a semiconductor wafer is applied to a sample stage whichis cooled and/or heated according to the desired temperature. In theprocess it is necessary to ensure that the temperature of thesemiconductor wafer does not drop below the dew point of the surroundinggaseous medium since otherwise moisture condenses on the surface of thewafer or icing occurs, which impedes or prevents the test measurements.

FIG. 5 shows a schematic cross-sectional view of a conditioning devicefor the purpose of explaining the problems on which the presentinvention is based.

In FIG. 4, reference symbol 1 designates a space in a container 5 inwhich a sample stage 10 which can be temperature controlled is providedand on which a semiconductor wafer (not shown) can be positioned fortest purposes. The volume of the container 5 is usually between 400 and800 litres.

The space 1 is enclosed essentially by the walls of the container 5which have bushings for electrical lines and media supply lines as wellas, if appropriate, bushings for probes which are to be attachedexternally and with which the test measurements semiconductor wafershown are to be carried out. However, this space 1 must not behermetically sealed by the container 5 depending on the application butmust at least be enclosed to such an extent that undesired penetrationof moist ambient air can be prevented by building up an internal excesspressure.

The sample stage 10 (also referred to as chuck) has a thermal insulation15 via which it is connected to a usually movable base 20. Acorresponding movement mechanism (not shown) is generally adjustable inthe X, Y and Z directions. If the movement mechanism is not located inthe container, a seal has to be provided between the base and container.

Furthermore, a heating device 90, which can be supplied from the outsidewith electrical current for heating purposes and which has a temperatureprobe (not shown), is integrated into the sample stage 10.

Reference symbol 100 designates a dew point sensor by means of which thedew point within the container 5 can be determined and which can supplya corresponding signal to a monitor 101 outside the container 5. The dewpoint sensor 100 is used in particular for the sake of reliability whenopening the device so that, for example, compensatory heating can becarried out in order to avoid condensation of water.

Furthermore, outflow elements 30 (oBdA. only two are shown) via whichdried air from outside, or a similar fluid such as, for example,nitrogen, can be introduced via a line r1 into the container in order todrive out moist ambient air from the container 5. This air is firstlyfed externally to an air drier 3 via a line r00 and then fed into theline r1.

A separate unit, which is connected to the container 5 via acorresponding electrical line 11 and a media supply line r2, is thetemperature control rack 2 which has the following devices.

Reference symbol 80 designates a temperature controller which canregulate the temperature of the sample stage 10 by heating by means ofthe heating device 90, the sample stage 10 simultaneously oralternatively being rinsed with air for cooling purposes, as isexplained in more detail below.

Reference symbol 70 designates a temperature regulating device to whichdried air is fed via the lines r0 and i1 from, for example, a gas bottleor from an air drier, and which has a heat exchanger 95 which isconnected to cooling assemblies 71, 72 by means of which it can becooled to a predetermined temperature.

The dried air which is fed via the lines r0, i1 is conducted through theheat exchanger 95 and then fed via the supply line r2 into the container5 to the sample stage 10, through which it crosses in correspondingcooling coils or cooling pipes (not shown). The dried air which hascooled the sample stage 10 leaves it via the line r3 and is conductedout of the container 5 to the atmosphere.

The dried air, which is conducted into the container 5 via the outflowelements 30 in order to condition the atmosphere of the container 5 isusually kept at room temperature so that only the surface of the samplestage 10 is kept at the desired measuring temperature, for example −20°C., but the other elements in the container 5 are approximately at roomtemperature. This dried air which is fed via the outflow elements 30flows out of the container 5 through slits or gaps (not shown) or aseparate outlet line.

The fact that a relatively high consumption of dried air occurs becausesaid air, on the one hand for conditioning the atmosphere and on theother hand for cooling the sample stage 10, is blown through thecontainer 5 and into the atmosphere, proves disadvantageous in thisknown device for conditioning semiconductor wafers. As a result, theconsumption of dried air is relatively high. A failure of the air drier3 also brings about immediate icing of the test wafer at correspondingtemperatures.

For this reason, the object of the present invention is to specify amethod and a device for conditioning semiconductor wafers and/orhybrids, which permit more efficient conditioning.

The method according to the invention having the features of claim 1 andthe corresponding device according to claim 9 have, in comparison withthe known solution approach, the advantage that the dried gas, forexample the dried air, can be used efficiently. Further advantages arethe high level of operational reliability and the fact that freedom fromice and condensation is ensured because the dry air leaving thewafer/hybrid holding device is always below the dew point of thetemperature at the wafer/hybrid holding device.

The idea on which the present invention is based is that at least aportion of the gas leaving the wafer/hybrid holding device is used tocondition the atmosphere within the space. In the present invention,cooling air is therefore used simultaneously at least partially as dryair. It is advantageous if the portion of gas is firstly heat-treatedand then allowed to flow out within the space.

For example, the portion is heat-treated outside a container and thenfed back to the container. A particular advantage of this example isthat a higher level of cooling efficiency is made possible bycorrespondingly feeding back the air from the sample stage to outsidethe container. In other words, the fed-back, cooled air can beadditionally used either for precooling the fed-in dried air or forcooling specific assemblies and not only for cooling the wafer/hybridholding device.

However, it is alternatively or additionally possible for a portion ofthe gas to be allowed to flow out within the container directly after itleaves the sample stage. Since it is not expedient to allow it to flowout directly at all temperatures, a corresponding regulating valve is tobe provided for this portion of gas.

Advantageous developments and improvements of the respective subjectmatter of the invention are given in the subclaims.

According to one preferred development, the line device has a first linevia which the fluid can be conducted from outside the space into thewafer/hybrid holding device, a second line via which the fluid can beconducted from the wafer/hybrid holding device to outside the space, anda third line via which the fluid can be fed back from outside the spaceinto the space. A temperature regulating device is provided between thesecond and third lines.

According to a further preferred development, outflow elements areprovided at the end of the third line.

According to a further preferred development, the line device has afirst line via which the fluid can be conducted from outside the spaceinto the wafer/hybrid holding device, and a fourth line via which thefluid can be conducted from the wafer/hybrid holding device into thespace.

According to a further preferred development, the line device has asecond line via which the fluid can be conducted from the wafer/hybridholding device to outside the space, and a third line via which thefluid can be fed back into the space from outside the space. Atemperature regulating device is provided between the second and thirdlines.

According to a further preferred development, a valve is provided forregulating the flow rate of the fourth line.

According to a further preferred development, the temperature regulatingdevice has a heating device.

According to a further preferred development, the temperature regulatingdevice has a heat exchanger to which at least a portion of the fluidleaving the space can be conducted.

According to a further preferred development, the heat exchanger is usedto precool the fed-in fluid.

According to a further preferred development, the line device isdesigned in such a way that the portion leaving the heat exchanger canbe fed back at least partially into the space in order to condition theatmosphere.

According to a further preferred development, a further line is providedvia which dry fluid can additionally be conducted directly into thespace from outside the space.

According to a further preferred development, the space is essentiallyenclosed by a container.

Exemplary embodiments of the invention are illustrated in drawings andwill be explained in more detail in the following description. In saiddrawings:

FIG. 1 is a schematic illustration of a first embodiment of theconditioning device according to the invention;

FIG. 2 is a schematic illustration of a second embodiment of theconditioning device according to the invention;

FIG. 3 is a schematic cross-sectional view of a third embodiment of theconditioning device according to the invention;

FIG. 4 is a schematic cross-sectional view of a fourth embodiment of theconditioning device according to the invention; and

FIG. 5 is a schematic cross-sectional view of a conditioning device forthe purpose of explaining the problems on which the present invention isbased.

In the figures, identical reference symbols designate identical orfunctionally identical components.

FIG. 1 is a schematic illustration of a first embodiment of theconditioning device according to the invention.

In what follows, components which have already been described above inconjunction with FIG. 5 will not be described again in order to avoidrepetitions.

Reference symbol 80′ designates a modified temperature controller whichcan not only regulate the temperature of the sample stage 10 by means ofthe heating device 90 but is also coupled to the dew point sensor 100via a line 12 and can thus initiate automatic compensatory heating whenthere is a risk of condensation of water/icing.

In the first embodiment according to FIG. 1, a heating device 105 isadditionally integrated into the temperature regulating device 70 and isnot in direct contact with the heat exchanger 95. Instead of ending atthe ambient atmosphere, the line r3 is conducted to the heating device105 so that the dry air which has left the sample stage 10 is, as itwere, fed back to the temperature control rack 2 and after it has passedthrough the heating device 105 it is conducted back via the line r4 tothe container 5 in which it flows out into the space 1 through outflowelements 40 for conditioning the atmosphere.

The reference symbol 4 designates a temperature sensor for sensing thetemperature in the space 1, which sensor supplies a correspondingtemperature signal TS to the temperature regulating device 70 which isused to regulate the temperature by means of the heating device 105.

By virtue of this arrangement, the dried air can fulfil a doublefunction, specifically firstly cool the sample stage 10 and thencondition the atmosphere of the space 1 before it is fed back to theambient atmosphere through openings in the container 5, and is thus usedmore effectively.

FIG. 2 is a schematic illustration of a second embodiment of theconditioning device according to the invention.

In the second embodiment according to FIG. 2, a line r5 branches offfrom the line r2 directly before the sample stage 10 and is alsoconducted through the sample stage 10 in the form of a cooling coil or acooling pipe, but then leaves the sample stage 10 at a different pointfrom that of the line r3 and from there via a controllable outlet valve45 which conducts corresponding dried air directly into the container 5after it leaves the sample stage 10.

Since this would lead to problems at very low temperatures in certainapplications, this option of conducting the dry gas via the line r5 intothe container 1 can be regulated by means of the outlet valve 45. Theregulation can be carried out in a customary way, for example by remotecontrol or in a wire-controlled fashion.

Otherwise the second embodiment is of identical design to the firstembodiment described above.

FIG. 3 shows a schematic cross-sectional view of a third embodiment ofthe conditioning device according to the invention.

Reference symbol 80′ designates a further modified temperaturecontroller which also controls the temperature regulating device 70 viathe control line ST and thus plays the role of a central temperaturecontrol system.

In the third embodiment according to FIG. 3, a portion of the dry airwhich is fed back via the line r3 is branched off before the heatingdevice 105 via line i3 and conducted through the heat exchanger 95 whereit contributes to the cooling in the same way as the dry air which isfreshly fed in via the lines r0, i1. The dry air leaves the heatexchanger 95 via the line i4, and directly after the heating device 105it is combined with the air which has flowed through the heating device105. From the corresponding junction point, this dried air is conducted,in precisely the same way as in the first embodiment, via the line r4and the outflow elements 40 into the container 5 for conditioning itsatmosphere.

Furthermore, this embodiment provides a controllable mixing valve 46 anda bypass line r10 by means of which the heat exchanger 95 can bebypassed.

The particular advantage of this embodiment is that a “residualcoldness” of the dried air which flows back from the sample stage 10 canbe used to cool the heat exchanger and at the same time can be fed backinto the container 5 after heating.

Otherwise, the second embodiment is constructed in the same way as thefirst embodiment described above.

FIG. 4 is a schematic cross-sectional view of a fourth embodiment of theconditioning device according to the invention.

Reference symbol 85 in FIG. 4 designates an additional gas-temperaturecontroller to which dry gas, for example dried air, is fed via lines r0,i2 from the same gas source as that of the heat exchanger 95, said airbeing placed at a predefined temperature by said controller and thenconducted into the interior of the container 5 via the line r1 and viathe outflow element 30.

The direct feeding in of dried air via the outflow element 30 in thecontainer 5 is therefore additionally provided in this embodiment but itcan also be configured in such a way that it can be switched off if thethroughflow rate through the sample stage 10 is completely sufficientfor conditioning the atmosphere within the container 5.

Although the present invention has been described above with referenceto preferred exemplary embodiments, it is not restricted to them butrather can be modified in a variety of ways.

In particular it is to be noted that the exemplary embodiments above canof course be combined with one another. Additional line connections andregulating valves for the respective gas flow, which can be controlledmanually or electrically, can also be provided.

In addition, the residual coldness of the fed-back gas can be used notonly for cooling the heat exchanger 95 but also for cooling any desiredother assemblies or heat exchangers before said residual coldness is fedback to the container 5.

The invention is also not restricted to gaseous dried air but can inprinciple be applied to any other fluids.

Furthermore, the wafer/hybrid holding device is not restricted to asample stage or chuck but rather can be varied as desired, for exampleas a clamp device or the like.

1. A method for conditioning semiconductor wafers and/or hybridscomprising: preparing a space which is essentially enclosed by acontainer and has a wafer/hybrid chuck which is located therein and hasthe purpose of holding a semiconductor wafer and/or hybrid applied tothe wafer/hybrid chuck; pre-cooling a dry fluid in a single heatexchanger outside the space; conducting the pre-cooled fluid out of thesingle heat exchanger into the wafer/hybrid chuck via a first line, andthen through the wafer/hybrid chuck to cool the wafer/hybrid chuck;conducting at least a portion of the fluid having been conducted throughthe wafer/hybrid chuck back to the single heat exchanger via a secondline out of the wafer/hybrid chuck to the single heat exchanger; andheating the portion, by using a residual coldness of the portion to coolthe single heat exchanger to contribute to the pre-cooling of the fluidin the single heat exchanger, wherein the heated portion is conductedvia a third line from the single heat exchanger into the space, beforebeing allowed to flow out within the space to condition the atmospherein the space, and wherein the same single heat exchanger both: pre-coolsand conducts the fluid to the wafer/hybrid chuck, and receives back thefluid from the wafer/hybrid chuck to contribute to the pre-cooling ofthe fluid.
 2. The method according to claim 1, wherein the portion isfirstly heat-treated and then allowed to flow out within the space. 3.The method according to claim 1, wherein the portion is heat-treatedoutside the space and then fed back to the space.
 4. The methodaccording to claim 1, wherein the portion is allowed to flow out withinthe space directly after it leaves the wafer/hybrid chuck.
 5. A methodfor conditioning semiconductor wafers and/or hybrids, comprising:preparing a space which is essentially enclosed by a container and has awafer/hybrid chuck which is located therein and has the purpose ofholding a semiconductor wafer and/or hybrid applied to the wafer/hybridchuck; pre-cooling a dry fluid in a single heat exchanger outside thespace; conducting the pre-cooled fluid out of the single heat exchangerinto the wafer/hybrid chuck via a first line, and then through thewafer/hybrid chuck to cool the wafer/hybrid chuck; wherein at least aportion of the fluid having been conducted through the wafer/hybridchuck is used to condition the atmosphere within the space; wherein afirst portion of the fluid having been conducted through thewafer/hybrid chuck is firstly conducted via a second line out of thewafer/hybrid chuck back to the single heat exchanger, then heated byusing a residual coldness of the first portion to cool the single heatexchanger to contribute to the pre-cooling of the fluid in the singleheat exchanger, and then conducted via a third line from the single heatexchanger into the space, before being allowed to flow out within thespace, wherein a second portion having been conducted through thewafer/hybrid chuck is allowed to flow out within the space directlyafter it leaves the wafer/hybrid chuck, and wherein the same single heatexchanger both: pre-cools and conducts the fluid to the wafer/hybridchuck, and receives back the fluid from the wafer/hybrid chuck tocontribute to the pre-cooling of the fluid.
 6. The method according toclaim 5, wherein at least one of the first and second portions can beregulated in terms of flow rate.
 7. The method according to claim 2,wherein the portion is heat-treated in that it is used for precoolingthe fluid, outside the space before said portion is allowed to flow outwithin the space.
 8. The method according to claim 1, wherein thepre-cooled fluid, when conducted through the wafer/hybrid chuck in orderto cool the wafer/hybrid chuck, crosses the wafer/hybrid chuck in acooling coil or cooling pipe.
 9. The method according to claim 5,wherein the pre-cooled fluid, when conducted through the wafer/hybridchuck in order to cool the wafer/hybrid chuck, crosses the wafer/hybridchuck in a cooling coil or cooling pipe.